Organic semiconductor device, organic solar cell, and display panel

ABSTRACT

An organic semiconductor device includes, between a pair of electrodes of a first metal electrode and a second electrode, at least, a light-emitting layer, a hole injection layer which removes holes from the first metal electrode, a hole transporting layer formed on the light-emitting layer on a side of the first metal electrode for transporting the holes removed by the hole injection layer to the light-emitting layer, and an electron transporting layer formed on the light-emitting layer on a side of the second electrode for removing electrons from the second electrode and transporting the electrons to the light-emitting layer, wherein the organic semiconductor device further includes a crystallinity controlling member which is a series of discontinuous clusters along the contact surface of the hole injection layer that is in contact with the first metal electrode, for controlling an orientation of crystalline molecules.

CROSS-REFERENCE TO RELATED APPLICATION

This is an application PCT/JP2007/75077, filed Dec. 27, 2007, which wasnot published under PCT article 21(2) in English.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic semiconductor device, etc.,that causes a light-emitting layer to emit light in accordance with anapplied voltage provided between a pair of electrodes.

2. Description of the Related Art

In recent years, the development of flat displays has blossomed. In suchflat displays, display devices that employ an organic semiconductordevice such as an organic electroluminescent device, etc., have becomecommonplace. Various studies have been conducted with the organicsemiconductor devices of recent years on the use of traditionallyemployed transparent electrodes such as ITO (indium tin oxide) as wellas a variety of other materials.

For example, in known organic semiconductor devices as shown in TheJournal of Vacuum Science and Technology A (July/August 2000), thereexists technology in which fullerene (C₆₀) and phthalocyanine (CuPc) arelayered on an electrode made of a metal material and formed on asubstrate to facilitate hole removal from the electrode. As a result, agreater number of holes are injected into the light-emitting layer,thereby reducing the driving voltage to be applied between the anode andcathode.

While the configuration of the above-described prior art contributes toa reduction in the driving voltage to a certain degree, a holetransporting layer that removes a great number of holes from the anodewith even greater efficiency, thereby enabling the organic semiconductordevice to operate under an even lower driving voltage has been desired.

SUMMARY OF THE INVENTION

The above-described problem is given as an example of the problems thatare to be solved by the present invention.

MEANS OF SOLVING THE PROBLEM

In order to achieve the above-described object, according to the firstinvention, there is provided an organic semiconductor device comprising:a first metal electrode, a hole injection layer, a hole transportinglayer, a light-emitting layer, an electron injection layer, and a secondelectrode layered in that order from a bottom layer on a substrate, thehole injection layer removing holes from the first metal electrode; thehole transporting layer supplying holes removed by the hole injectionlayer to the light-emitting layer; and the electron injection layerremoving electrons from the second electrode and supplies the electronsto the light-emitting layer; wherein: the organic semiconductor devicefurther comprises a crystallinity controlling member which is a seriesof discontinuous clusters along a contact surface of the hole injectionlayer in contact with the first metal electrode, for controlling anorientation of crystalline molecules of the hole injection layer; thecrystallinity controlling member is cohesion molecules that differ frommolecules of the material constituting the hole injection layer; andeach of the crystalline molecules has an orientation greater than orequal to 1 degree and less than or equal to 90 degrees with respect tothe substrate.

In order to achieve the above-described object, according to the 14thinvention, there is provided an organic solar cell comprising: a firstmetal electrode, a photoelectric conversion layer, an electrontransporting layer, and a second electrode layered in that order from abottom layer on a substrate, the photoelectric conversion layerseparating exciters generated on a boundary surface between a P-typematerial and an N-type material that absorb light into holes andcharges; and the electron transporting layer removing the charges fromthe photoelectric conversion layer and transports the charges to thesecond electrode; wherein: the organic solar cell further comprises acrystallinity controlling member which is a series of discontinuousclusters along a contact surface of the photoelectric conversion layerin contact with the first metal electrode, for controlling anorientation of crystalline molecules of the photoelectric conversionlayer; the crystallinity controlling member is cohesion molecules thatdiffer from the molecules of the material constituting the electrontransporting layer; and each of the crystalline molecules has anorientation greater than or equal to 1 degree and less than or equal to90 degrees with respect to the substrate.

In order to achieve the above-described object, according to the 15thinvention, there is provided a display panel comprising an organicsemiconductor device comprising: a first metal electrode, a holeinjection layer, a hole transporting layer, a light-emitting layer, anelectron injection layer, and a second electrode layered in that orderfrom a bottom layer on a substrate, the hole injection layer removingholes from the first metal electrode; the hole transporting layersupplying holes removed by the hole injection layer to thelight-emitting layer; and the electron injection layer removingelectrons from the second electrode and supplies the electrons to thelight-emitting layer; wherein: the organic semiconductor device furthercomprises a crystallinity controlling member which is a series ofdiscontinuous clusters along a contact surface of the hole injectionlayer in contact with the first metal electrode, for controlling anorientation of crystalline molecules of the hole injection layer; thecrystallinity controlling member is cohesion molecules that differ fromthe molecules of the material constituting the hole injection layer; andeach of the crystalline molecules has an orientation greater than orequal to 1 degree and less than or equal to 90 degrees with respect tothe substrate.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a partial cross-sectional view illustrating a configurationexample of the organic electroluminescent device of the display panel ofembodiment 1, as enlarged.

FIG. 2 is a cross-sectional view illustrating a configuration example ina case where the specific range shown in FIG. 1 is enlarged.

FIG. 3 is a cross-sectional view illustrating a configuration example ina case where the specific range shown in FIG. 1 is enlarged.

FIG. 4 is a cross-sectional view illustrating a configuration example ina case where the specific range shown in FIG. 1 is enlarged.

FIG. 5 is a cross-sectional view illustrating a configuration example ina case where the specific range shown in FIG. 1 is enlarged.

FIG. 6 is a cross-sectional view illustrating a configuration example ina case where the specific range shown in FIG. 1 is enlarged.

FIG. 7 is a cross-sectional view illustrating a configuration example ina case where the specific range shown in FIG. 1 is enlarged.

FIG. 8 is a diagram illustrating an example of the verification resultsof orientation control by X-ray diffraction.

FIG. 9 is a diagram illustrating an example of the verification resultsof orientation control by X-ray diffraction.

FIG. 10 is a diagram illustrating an example of the verification resultsof orientation control by X-ray diffraction.

FIG. 11 is a table illustrating an example of the verification resultsof the driving voltage of the organic electroluminescent device.

FIG. 12 is a table illustrating an example of the verification resultsof the driving voltage of the organic electroluminescent device.

FIG. 13 is a table illustrating a verification example of surfaceroughness of the anode on the glass substrate, and of each case ofcohesion molecules that exist on that anode.

FIG. 14 is a diagram illustrating an example of the voltage and currentdensity characteristics of the organic solar cell of embodiment 2.

FIG. 15 is a diagram illustrating an example of the voltage and currentdensity characteristics of a general organic solar cell.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following describes an embodiment of the present invention withreference to accompanying drawings.

Embodiment 1

FIG. 1 is a partial cross-sectional view illustrating an example of acase where an organic semiconductor device of embodiment 1 is applied toan organic electroluminescent device 3 of a display panel.

The organic electroluminescent device 3 is an example of an organicsemiconductor device, and is formed correspondingly to the colors red,green, and blue, for example. The organic electroluminescent device 3shown in the figure is for one pixel section.

This organic electroluminescent device 3 is structured so that an anode46, a hole injection layer 47, a hole transporting layer 48, alight-emitting layer 49, an electron injection layer 51, and a cathode52 are layered in that order on a glass substrate 45. Note that theorganic electroluminescent device 3 may employ a structure wherein anelectric charge and exciter diffusion layer for capturing an electriccharge and exciter within the light-emitting layer 49 is layered.

The glass substrate 45 is formed by a transparent, semitransparent, ornon-transparent material. The above-described anode 46 is formed tocover the glass substrate 45. This anode 46 has a function of supplyingholes to the light-emitting layer 49 described later. The anode 46 maybe made of a material other than the aforementioned Au as well, such asAg, Cu, ITO (indium tin oxide), or IZO (indium zinc oxide), for example.Further, the anode 46 may also employ Al, Mo, or Ti, for example. Inthis embodiment, the anode 46 is a metal electrode mainly made of Au.

The hole injection layer 47 has a function of facilitating the removalof holes from the anode 46. This hole injection layer 47 has crystallinemolecules 9 of a material such as CuPc or pentacene, for example. Thesecrystalline molecules 9 will be described later. The above-describedhole transporting layer 48 has a function of transporting the holesremoved from the anode 46 by the hole injection layer 47 to thelight-emitting layer 49. The hole transporting layer 48 is made of amaterial such as NPB (amorphous), for example.

The hole transporting layer 48 exists between the hole injection layer47 and the light-emitting layer 49, and has a function of suppressing adecrease in brightness of the light emitted by the light-emitting layer49 by thus separating the hole injection layer 47 and the light-emittinglayer 49. This suppression occurs because energy no longer moves to thehole injection layer 47 made of a CuPc material which absorbs energy(exciters) generated within the light-emitting layer 49 in the visibleregion (that is, that has a small energy gap), making it difficult forbrightness to decrease. This holds true for cases where the holeinjection layer 47 is made of pentacene as well. Note that even if thereis a large energy gap with the crystalline molecules 9 of the holeinjection layer 47, such a decrease in brightness does not readilyoccur. The hole transporting layer 48 is made of a material such as NPB,for example, thereby preventing a decrease in brightness owing to thelarge energy gap from Alq₃. That is, the aforementioned holetransporting layer 48 is made of the material NPB, which is generallyused as a hole transportable material having hole mobility and, in thisembodiment, fulfills the function of improving luminous efficiency andserving as a suppression layer.

The above-described light-emitting layer 49 is a light-emitting devicethat is made of an organic material, for example, and employs aso-called electroluminescence (EL) phenomenon. The light-emitting layer49 is layered between any of the layers between the plurality ofelectrodes 46 and 52, and has a function of emitting light by anelectric field generated between the plurality of electrodes 46 and 52by an applied voltage. This light-emitting layer 49 outputs its ownlight by utilizing a phenomenon in which light is emitted based onenergy received from an external source using an electric field.

In this embodiment, this light-emitting layer 49 is described as a layerhaving a function of a so-called electron transporting layer as well.Here, a function of an electron transporting layer refers to a functionof efficiently transporting the electrons removed from the cathode 52 bythe electron injection layer 51 to the light-emitting layer 49. Notethat an electron transporting layer separate from the light-emittinglayer 49 may be independently formed between the light-emitting layer 49and the electron injection layer 51 rather than provided as a functionof the light-emitting layer 49.

The electron injection layer 51 is stacked on the light-emitting layer49. This electron injection layer 51 has a function of facilitatingremoval of electrons from the cathode 52. The cathode 52 is formed onthe electron injection layer 51. Note that the electron injection layer51 may also include a function of a buffer layer or the cathode 52. Inthe organic electroluminescent device 3, the light-emitting layer 49outputs visible light by an electric field in accordance with thevoltage applied between the anode 46 and the cathode 52.

In the organic electroluminescent device 3, a crystallinity controllingmember 8 exists along the top surface of the hole injection layer 47that is in contact with the anode 46. In this embodiment, the existenceof this crystallinity controlling member 8 improves the injection rate,and decreases the driving voltage and/or extends the service life of thedevice, for example.

This crystallinity controlling member 8 has a function of controllingthe orientation of an organic semiconductor material having planarity,for example. The crystallinity controlling member 8 is a series ofdiscontinuous clusters along the contact surface of the hole injectionlayer 47 that is in contact with the anode 46 (first metal electrode),and is a member that controls the orientation of the crystallinemolecules 9 described later.

Here, the “series of discontinuous clusters” may refer to a structurehaving an uneven shape, for example. The crystallinity controllingmember 8, as such a series of clusters, may be a cluster object or film.That is, the “series of discontinuous clusters” may be a thin filmhaving a rate of coverage of the surface of the anode 46 of greater thanor equal to 1% to less than 100%.

The crystallinity controlling member 8 has a function of controlling theorientation of planar molecules and/or rod-shaped molecules, which areemployed as examples of crystalline molecules 9 on the top surface ofthe hole injection layer 47, thereby controlling the orientation ofthese crystalline molecules 9. The crystallinity controlling member 8thus controls the orientation of the crystalline molecules 9,facilitating removal of holes from the anode 46 and, in turn, making itpossible to decrease the driving voltage to be applied between the anode46 and the cathode 52.

FIGS. 2 to 7 are each a cross-sectional view illustrating aconfiguration example in a case where a specific range W illustrated inFIG. 1 is enlarged. Note that the layer configuration illustrated inFIGS. 2 to 7 shows each layer having a thickness that differs fromactually for clarity of explanation.

FIG. 2 to FIG. 4 illustrate a state in which a cohesion matter 5 havinga cross-sectional shape of a mountain is incorporated as the series ofdiscontinuous clusters that serves as the crystallinity controllingmember, and FIG. 5 to FIG. 7 illustrate a state in which a cohesionmatter 7 having a cross-sectional shape of a circle is incorporated asthe series of discontinuous clusters that serves as the crystallinitycontrolling member.

First, the aforementioned crystallinity controlling member 8 is thecohesion matter 5 incorporated to form an uneven shape on the topsurface of the hole injection layer 47, for example. In this embodiment,cohesion molecules that differ from the molecules of the material thatforms the hole injection layer 47, for example, are used as the cohesionmatter 5. Examples of the material used to form the hole injection layer47 include a hole injection material such as pentacene. On the otherhand, either molybdenum oxide (MoO₃), C₆₀ (fullerene) or Alq₃ may bealternatively selected as the cohesion molecules.

That is, MoO₃ (molybdenum oxide) may be incorporated, or C₆₀ (fullerene)may be incorporated, or Alq₃ may be incorporated as the cohesionmolecules in the hole injection layer 47.

In FIG. 2, planar or bar-shaped crystalline molecules 9 are disposedalong the anode 46 on the top surface of the hole injection layer 47facing the anode 46. The orientation of each crystalline molecule 9 iscontrolled by the cohesion matter 5 so that the angular orientation withrespect to the substrate 45 is θ1. That is, the crystallinity of eachcrystalline molecule 9 is controlled. The crystalline molecule 9 that isthus orientation-controlled has an orientation greater than or equal to1 degree and less than or equal to 90 degrees with respect to thesubstrate 45.

The cohesion matter 5 has a discontinuous film shape when viewed in itsentirety, and a thickness of about a thickness T. The thickness T is,for example, about 0.1 nm to 10 nm. The cohesion matter 5 changes shapewhen the cohesion molecules are incorporated in accordance with atleast, for example, one of the following conditions: molecular size,cohesive force, affinity for the top surface of the first metalelectrode 46, and coverage. The molecular size referred to here is, forexample 0.1 nm (1 {acute over (Å)}) or greater. Further, the materialemployed as the organic semiconductor material thusorientation-controlled may be a material having minimal intermolecularspacing, such as 0.1 [nm] (1 {acute over (Å)}) for example, and uniformcrystallinity.

The cohesion molecules are self-cohered, even if the material has asmall molecular size, for example, making it possible to form astructure having a coverage greater than or equal to 1% and less than100%. When the coverage of the first metal electrode 46 by the cohesionmolecules is thus less than 100%, the cohesion molecules does not coverthe entire surface of the first metal electrode 46, causing electricalcontact to remain between the first metal electrode 46 and the electrontransporting layer 50, thereby maintaining the flow of electric current.

Further, when there is affinity for the top surface of the first metalelectrode 46, the cohesion molecules and the first metal electrode 46have affinity for one another, thereby improving wettability and causingthe cohesion molecules to readily become familiar with the first metalelectrode 46 and increase smoothness. On the other hand, if there isaffinity and hydrophobic properties between the cohesion molecules andthe first metal electrode 46, wettability is poor, making it easier toform a film structure having a coverage greater than or equal to 1% andless than 100%.

In FIG. 3, while the crystalline molecules 9 are similarly disposedalong the anode 46, the angular orientation θ1 is smaller than the caseof FIG. 5 due to the small size of the incorporated cohesion matter 2.In FIG. 4 as well, while the crystalline molecules 9 are similarlydisposed along the anode 46, the angular orientation θ1 is even smallerthan the case of FIG. 3 due to the even smaller size of the incorporatedcohesion matter 5.

In FIG. 5, planar or bar-shaped crystalline molecules 9 are disposedalong the anode 46 on the top surface of the hole injection layer 47facing the anode 46. The orientation of each of the crystallinemolecules 9 is controlled by the cohesion matter 5 having asubstantially circular cross-sectional shape so that the angularorientation with respect to the substrate 45 is θ1. That is, thecrystallinity of each crystalline molecule 9 is controlled.

In FIG. 6, while the crystalline molecules 9 are similarly disposedalong the anode 46, the angular orientation θ1 is smaller than the caseof FIG. 5 due to the small size of the incorporated cohesion matter 5.In FIG. 7 as well, while the crystalline molecules 9 are similarlydisposed along the anode 46, the angular orientation θ1 is even smallerthan the case of FIG. 6 due to the even smaller size of the incorporatedcohesion matter 5.

An example of the verification results of the driving voltage of theorganic electroluminescent device 3 will now be described with referenceto FIG. 1 to FIG. 7, with the organic electroluminescent device 3 builtinto the display panel having a configuration such as described in theexample above.

Verification of Orientation Control by X-Ray Diffraction

FIG. 8 to FIG. 10 each illustrate an example of verification results oforientation control by X-ray diffraction. Note that the horizontal axisindicates the X-ray angle of incidence 2θ/ω [deg], and the vertical axisindicates intensity [counts]. In these figures, orientation ispreferably controlled at an X-ray angle of incidence of 2θ/ω [deg] inthe section where the peak occurs. Note that while this embodiment isdescribed in connection with an illustrative scenario in which thesubstrate is the aforementioned glass substrate 45, the substrate may bea material such as Si, for example.

When the Crystalline Molecule 9 Contains CuPc

Orientation control characteristics F10 shown in FIG. 8 represent a casewhere Au (gold) and CuPc are used as the materials for the anode 46formed on the glass substrate 45, and NPB is used as the material forthe hole transporting layer 48. Note that the materials of the layercomponents other than those of the hole transporting layer 48, etc., arethe same as those described above, and descriptions of the verificationof orientation control thereof will be omitted. In order to explain thesuperiority of this embodiment, the orientation control characteristicsF10 represent the orientation characteristics in a case where a knownlayer configuration is employed, and a peak does not appear.

On the other hand, orientation control characteristics F11 represent acase where Au (gold) is used as the materials for the anode 46 formed onthe glass substrate 45, C₆₀ and CuPc are respectively used as thematerials for the cohesion molecule 7 and the crystalline molecule 9 ofthe crystallinity controlling member 8, and NPB is used as the materialfor the hole transporting layer 48. Note that the materials of the layercomponents after the hole transporting layer 48 are the same as thosedescribed above, and descriptions of the verification thereof will beomitted. The orientation control characteristics F11 represent a casewhere the layer component of the crystallinity controlling member 8 ofthis embodiment is employed. With the orientation controlcharacteristics F11, a peak appears when the X-ray angle of incidence2θ/ω is approximately 6.84 [deg]. At this time, the crystalline molecule9 of the crystallinity controlling member 8 is positioned in a verticaldirection with respect to the glass substrate 45, indicating that theorientation of the crystalline molecule 9 is well controlled.

Further, orientation control characteristics F12 shown in FIG. 9represent a case where Au (gold) is used as the material for the anode46, MoO3 and CuPc are respectively used as the materials for thecohesion molecule 7 and the crystalline molecule 9 of the crystallinitycontrolling member 8, and NPB is used as the material for the holetransporting layer 48. The orientation control characteristics F12represent a case where the layer component of the crystallinitycontrolling member 8 of this embodiment is employed. With theorientation control characteristics F12, a peak appears when the X-rayangle of incidence 2θ/ω is approximately 6.8 [deg]. At this time, thecrystalline molecule 9 of the crystallinity controlling member 8 ispositioned in a vertical direction with respect to the glass substrate45, indicating that the orientation of the crystalline molecule 9 iswell controlled.

Further, orientation control characteristics F13 shown in FIG. 9represent a case where Au (gold) is used as the material for the anode46, Alq₃ and CuPc are respectively used as the materials for thecohesion molecule 7 and the crystalline molecule 9 of the crystallinitycontrolling member 8, and NPB is used as the material for the holetransporting layer 48. The orientation control characteristics F13represent a case where the layer component of the crystallinitycontrolling member 8 of this embodiment is employed. With theorientation control characteristics F13, a peak appears when the X-rayangle of incidence 2θ/ω is approximately 6.8 [deg]. At this time, thecrystalline molecule 9 of the crystallinity controlling member 8 ispositioned in a vertical direction with respect to the glass substrate45, indicating that the orientation of the crystalline molecule 9 iswell controlled.

When the Crystalline Molecule 9 Contains Pentacene

Orientation control characteristics F20 shown in FIG. 10 represent acase where Au (gold) and pentacene are used as the materials for theanode 46, and NPB is used as the material for the hole transportinglayer 48. In order to explain the superiority of this embodiment, theorientation control characteristics F20 indicate the orientationcharacteristics in a case where a known layer configuration is employed,and a peak does not appear.

On the other hand, with orientation control characteristic F21, Au(gold) is used as the material for the anode 46, C₆₀ and pentacene arerespectively used as the materials for the cohesion molecule 7 and thecrystalline molecule 9 of the crystallinity controlling member 8, andNPB is used as the material for the hole transporting layer 48. Theorientation control characteristics F21 represent a case where the layercomponent of the crystallinity controlling member 8 of this embodimentis employed. With the orientation control characteristics F21, a peakappears when the X-ray angle of incidence 2θ/ω is approximately 6.84[deg]. At this time, the crystalline molecule 9 of the crystallinitycontrolling member 8 is positioned in a vertical direction with respectto the glass substrate 45, indicating that the orientation of thecrystalline molecule 9 is well controlled.

Further, orientation control characteristics F22 shown in FIG. 10represent a case where Au (gold) is used as the material for the anode46, MoO₃ and pentacene are respectively used as the materials for thecohesion molecule 7 and the crystalline molecule 9 of the crystallinitycontrolling member 8, and NPB is used as the material for the holetransporting layer 48. The orientation control characteristics F22represent the layer component of the crystallinity controlling member 8of this embodiment. With the orientation control characteristics F22, apeak appears when the X-ray angle of incidence 2θ/ω is approximately 6.8[deg]. At this time, the crystalline molecule 9 of the crystallinitycontrolling member 8 is positioned in a vertical direction with respectto the glass substrate 45, indicating that the orientation of thecrystalline molecule 9 is well controlled.

Further, orientation control characteristics F23 shown in FIG. 10represent a case where Au (gold) is used as the material for the anode46, Alq₃ and pentacene are respectively used as the materials for thedissimilar molecule 7 and the crystalline molecule 9 of thecrystallinity controlling member 8, and NPB is used as the material forthe hole transporting layer 48. The orientation control characteristicsF23 represent a case where the layer component of the crystallinitycontrolling member 8 of this embodiment is employed. With theorientation control characteristics F23, a peak appears when the X-rayangle of incidence 2θ/ω is approximately 6.8 [deg]. At this time, thecrystalline molecule 9 of the crystallinity controlling member 8 ispositioned in a vertical direction with respect to the glass substrate45, indicating that the orientation of the crystalline molecule 9 iswell controlled.

Verification of Driving Voltage

FIG. 11 and FIG. 12 are tables respectively showing examples of theverification results of the driving voltage of the organicelectroluminescent device 3. In FIG. 11 and FIG. 12, the illustrativeexamples use phthalocyanine (CuPc) and pentacene, respectively, as thematerial of the crystalline molecule 9.

These verifications verify how the driving voltage changes in accordancewith the combination of the material of the crystalline molecules 9 andthe material of the cohesion molecules, under the verificationconditions described later.

In the illustrative examples, the materials used for the crystallinemolecules 9 include phthalocyanine (CuPc) and pentacene as describedabove, and the cohesion molecules of each of the cases of the cohesionmatters 5 and 7 are as follows: (1) non-existent, (2) molybdenum oxide(MoO₃), (3) fullerene (C₆₀), and (4) Alq₃.

Verification Conditions

In these verifications, the illustrative examples of the film thicknessof each layer are as follows.

First, the film thickness of the anode 46 (first metal electrode) iswithin the range of 1 nm to 40 nm, and is 20 nm in this example. Thethickness of the cohesion molecule 7 and the crystalline molecule 9 ofthe orientation controlling member is 3 nm, the film thickness of thecrystalline molecule 9 is 15 nm, the film thickness of the holetransporting layer 48 is 35 nm, and the film thickness of thelight-emitting layer 49 is 60 nm. The film thickness of the electroninjection layer 51 is 1 nm, and the film thickness of the cathode 52(second electrode) is 80 nm. Note that the current density is, forexample, 7.5 [mA/cm²], and the brightness of the light-emitting layer 49is at a similar level in each of the verifications.

For the verification results shown in FIG. 11 and FIG. 12, the materialsemployed for each layer include gold (Au) for the anode 46,phthalocyanine (CuPc), etc., for the crystalline molecule 9, Alq₃ forthe light-emitting layer 49, LiO₂ for the electron injection layer 51,and aluminum (Al) for the cathode 52.

According to the verification results shown in FIG. 11, the drivingvoltage of the organic electroluminescent device 3 is as follows.

(1) In a case where the cohesion molecules are non-existent, the drivingvoltage of the organic electroluminescent device 3 is 13.8 [V].Hereinafter, this driving voltage will be referred to as the “referencedriving voltage.” Conversely, (2) in a case where the material of thecohesion molecules is molybdenum oxide (MoO₃), the driving voltage ofthe organic electroluminescent device 3 is 5.7 [V]. (3) In a case wherethe material of the cohesion molecules is fullerene (C₆₀), the drivingvoltage of the organic electroluminescent device 3 is 5.8 [V]. (4) In acase where the material of the cohesion molecules is Alq₃, the drivingvoltage of the organic electroluminescent device 3 is 10.1 [V].

Thus, the driving voltage in a case where Alq₃ is employed as thematerial of the cohesion molecules is lower than the aforementionedreference voltage, making the organic electroluminescent device 3 havehigher luminous efficiency as a whole. Further, the driving voltage inthe case where fullerene (C₆₀) is used as the material of the cohesionmolecules is significantly lower than the driving voltage in the casewhere Alq₃ is used as the material of the cohesion molecules. Further,the driving voltage in the case where molybdenum (MoO₃) is used as thematerial of the cohesion molecules is lower than the driving voltage inthe case where fullerene (C₆₀) is used as the material of the cohesionmolecules.

Thus, the organic electroluminescent device 3 shows a reduction in thedriving voltage in the order of Alq₃, fullerene (C₆₀), and molybdenum(MoO₃) as the material of the cohesion molecules.

Note that, in an illustrative scenario where C₆₀ is used as the cohesionmolecules under the same conditions as those indicated in FIG. 11excluding the fact that the anode 46 is made of silver (Ag), the drivingvoltage is 5.6 [V].

The brightness will now be simply explained. According to theverification results shown in FIG. 11, the brightness of the organicelectroluminescent device 3 is as follows.

(1) In a case where cohesion molecules are non-existent, the brightnessof the organic electroluminescent device 3 is 270 [cd/m²]. Conversely,(2) in a case where the material of the cohesion molecules is molybdenumoxide (MoO₃), the brightness of the organic electroluminescent device 3is 339 [cd/m²]. (3) In a case where the material of the cohesionmolecules is fullerene (C₆₀), the brightness of the organicelectroluminescent device 3 is 334 [cd/m²]. (4) In a case where thematerial of the cohesion molecules is Alq₃, the brightness of theorganic electroluminescent device 3 is 385 [cd/m²].

On the other hand, according to the verification results shown in FIG.12, the driving voltage of the organic electroluminescent device 3 is asfollows.

(1) In a case where cohesion molecules are non-existent, the drivingvoltage of the organic electroluminescent device 3 is 9.1 [V].Hereinafter, this driving voltage will be referred to as the “referencedriving voltage.” In comparison to this reference driving voltage, (2)in a case where the material of the cohesion molecules is molybdenumoxide (MoO₃), the driving voltage of the organic electroluminescentdevice 3 is 3.9 [V]. (3) In a case where the material of the cohesionmolecules is fullerene (C₆₀), the driving voltage of the organicelectroluminescent device 3 is 4.4 [V]. (4) In a case where the materialof the cohesion molecules is Alq₃, the driving voltage of the organicelectroluminescent device 3 is 9.4 [V].

Thus, the driving voltage in the case where fullerene (C₆₀) is used asthe material of the cohesion molecules is significantly lower than thedriving voltage in the case where Alq₃ is used as the material of thecohesion molecules. Further, the driving voltage in the case wheremolybdenum (MoO₃) is used as the material of the cohesion molecules islower than the driving voltage in the case where fullerene (C₆₀) is usedas the material of the cohesion molecules.

Thus, the organic electroluminescent device 3 shows a reduction in thedriving voltage in the order of Alq₃, fullerene (C₆₀), and molybdenum(MoO₃) as the material of the cohesion molecules.

The brightness will now be simply explained. According to theverification results shown in FIG. 12, the brightness of the organicelectroluminescent device 3 is as follows.

(1) In a case where cohesion molecules are non-existent, the brightnessof the organic electroluminescent device 3 is 50 [cd/m²]. Conversely,(2) in a case where the material of the cohesion molecules is molybdenumoxide (MoO₃), the brightness of the organic electroluminescent device 3is 241 [cd/m²]. (3) In a case where the material of the cohesionmolecules is fullerene (C₆₀), the brightness of the organicelectroluminescent device 3 is 265 [cd/m²]. (4) In a case where thematerial of the cohesion molecules is Alq₃, the brightness of theorganic electroluminescent device 3 is 371 [cd/m²].

Verification of Surface Roughness

FIG. 13 is a table showing a verification example of a surface roughnessRa of the anode 46 on the glass substrate 45 and of each case wherecohesion molecules exist on the anode 46. Note that in FIG. 13 the glasssubstrate 45 is omitted. In this verification example, the anode 46 ismade of gold and has a film thickness of 20 [nm], and the thickness ofeach of the cohesion molecules is 3 [nm].

First, (1) in a case where cohesion molecules do not exist on the anode46, the surface roughness Ra of the anode 46 is 2.6 [nm]. Hereinafter,this surface roughness will be referred to as the “reference surfaceroughness.” In comparison with this reference surface roughness, (2) ina case where the material of the cohesion molecules on the anode 46 ismolybdenum oxide (MoO₃), the surface roughness Ra is 9.3 [nm]. (3) In acase where the material of the cohesion molecules on the anode 46 isfullerene (C₆₀), the surface roughness Ra is 6.5 [nm]. (4) In a casewhere the material of the cohesion molecules on the anode 46 is Alq₃,the surface roughness Ra is 3.5 [nm].

The surface shape differs in accordance with the type of the material ofthe cohesion molecules on the anode 46. Regardless of material type,however, the grain size is smaller than that of the Au top surface. Thesurface roughness Ra increases by a multiplication factor of about 1.3to 3.6 with the insertion of cohesion molecules having a thickness ofabout 3 nm. Referring to these values of the surface roughness Ra thatoccurred in accordance with the incorporated cohesion molecules, thedriving voltage of the organic electroluminescent device 3 is inverselyproportional to the surface roughness Ra. That is, it is understoodthat, with the organic electroluminescent device 3, the surfaceroughness Ra, which occurs as a result of the incorporation of cohesionmolecules, increasingly contributes to a decrease in driving voltage asit increases.

The organic semiconductor device 3 of the above-described embodimentincludes, between a pair of electrodes of the first metal electrode 46(anode) and the second electrode 52 (cathode), at least, thelight-emitting layer 49, the hole injection layer 47 which removes holesfrom the first metal electrode 46, the hole transporting layer 48 formedon a side of the first metal electrode 46 from the light-emitting layer49 for transporting the holes removed by the hole injection layer 47 tothe light-emitting layer 49, and the electron injection layer 51 formedon a side of the second electrode 52 from the light-emitting layer 49for removing the electrons from the second electrode and supplying theelectrons thus removed to the light-emitting layer, wherein the organicsemiconductor device 3 comprises the crystallinity controlling member 8(cohesion matter, cohesion molecules) which is a series of discontinuousclusters along the top surface of the hole injection layer 47 in contactwith the first metal electrode 46, for controlling the orientation ofthe crystalline molecules 9.

With this arrangement, the crystallinity controlling member 8 (5, 7)controls the orientation in accordance with the surface roughness of theuneven top surface of the hole injection layer 47 that is positionedalong the surface that comes in contact with the first metal electrode46. As a result, holes are removed from the first metal electrode 46 andmore readily moved to the hole injection layer 47, making it possible todecrease the overall driving voltage of the organic semiconductor device3 to a greater degree than in prior art. Further, since the organicsemiconductor device 3 operates at a low driving voltage, the burdenplaced on the device itself is alleviated, thereby extending the servicelife of the device further than that of prior art.

Further, in the organic semiconductor device 3 of the above-describedembodiment, in addition to the aforementioned configuration, thecrystallinity controlling member 8 controls the crystal orientation ofthe planar molecules and/or bar-shaped molecules of the crystallinemolecules 9.

With this arrangement, the crystallinity controlling member 8 controlsthe orientation of the planar molecules and/or the bar-shaped molecules,thereby suppressing the driving voltage.

Further, in the organic semiconductor device 3 of the above-describedembodiment, in addition to the aforementioned configuration, thecrystallinity controlling member 8 is the cohesion matter 5 or 7incorporated to form an uneven shape on the top surface of the holeinjection layer 47.

With this arrangement, the crystallinity controlling member 5 or 7adjusts the surface roughness of the first metal electrode 46 and thehole injection layer 47 in accordance with the incorporated cohesionmatter 5 or 7, making it possible to control the orientation of thecrystalline molecules 9 and reduce the driving voltage.

Further, in the organic semiconductor device 3 of the above-describedembodiment, in addition to the aforementioned configuration, thecrystallinity controlling member 8 is made of cohesion molecules thatdiffer from the molecules of the material constituting the holeinjection layer 47.

With this arrangement, the crystallinity controlling member 5 or 7adjusts the surface roughness of the first metal electrode 46 and thehole injection layer 47 in accordance with the incorporated cohesionmolecules, making it possible to control the orientation of thecrystalline molecules 9 and reduce the driving voltage.

Further, in the organic semiconductor device 3 of the above-describedembodiment, in addition to the aforementioned configuration, MoO₃(molybdenum oxide) is incorporated as the cohesion molecules.

When MoO₃ is thus included in the crystallinity controlling member, thesurface roughness of the top surface of the first metal electrode 46(anode) increases, making it possible to suppress the driving voltage tobe applied between the first metal electrode 46 and the second electrode52 to a greater degree than in prior art. Additionally, when MoO₃ isused as the material for the crystallinity controlling member 8, theHOMO level or LUMO level of the MoO₃ molecules approaches the HOMO levelor LUMO level of the pentacene molecules and the HOMO level or LUMOlevel of the first metal electrode 46 molecules, thereby making itpossible to suppress the driving voltage.

Further, in the semiconductor device 3 of the above-describedembodiment, in addition to the aforementioned configuration, C₆₀(fullerene) is incorporated as the cohesion molecules.

When C₆₀ is thus included in the crystallinity controlling member, thesurface roughness of the top surface of the first metal electrode 46increases, making it possible to suppress the driving voltage to beapplied between the first metal electrode 46 and the second electrode 52to a greater degree than in prior art. Additionally, when C₆₀ is used asthe material for the crystallinity controlling member 8, the HOMO levelor LUMO level of the C₆₀ molecules approaches the HOMO level or LUMOlevel of the pentacene molecules and the HOMO level or LUMO level of thefirst metal electrode 46 molecules, thereby making it possible tosuppress the driving voltage.

In the semiconductor device 3 of the above-described embodiment, Alq₃ isincorporated as the cohesion molecules.

When Alq₃ is thus included in the crystallinity controlling member 8,the surface roughness of the top surface of the first metal electrode 46increases, making it possible to suppress the driving voltage to beapplied between the first metal electrode 46 and the second electrode 52to a greater degree than in prior art. Additionally, when Alq₃ is usedas the material for the crystallinity controlling member, the HOMO levelor LUMO level of the Alq₃ molecules approaches the HOMO level or LUMOlevel of the pentacene molecules and the HOMO level or LUMO level of thefirst metal electrode 46 molecules, thereby making it possible tosuppress the driving voltage.

Further, in the organic semiconductor device 3 of the above-describedembodiment, in addition to the aforementioned configuration, the firstmetal electrode 46 is gold, silver, or copper.

With this arrangement, when gold, etc., is used for the first metalelectrode 46, the orientation of the crystalline molecules 9 isfavorably controlled, making it possible to decrease the drivingvoltage.

Further, in the organic semiconductor device 3 of the above-describedembodiment, in addition to the aforementioned configuration, the holeinjection layer 47 contains CuPc.

With this arrangement, the driving voltage to be applied between thefirst metal electrode 46 and the second electrode 52 decreases, makingit possible to extend the service life of the organic semiconductordevice 3.

Further, in the organic semiconductor device 3 of the above-describedembodiment, in addition to the aforementioned configuration, the holeinjection layer 47 contains pentacene.

With this arrangement, the driving voltage to be applied between thefirst metal electrode 46 and the second electrode 52 decreases, makingit possible to extend the service life of the organic semiconductordevice 3.

Further, the organic semiconductor device 3 of the above-describedembodiment, in addition to the aforementioned configuration, comprisesthe substrate 45 on which is layered the first metal electrode 46, thehole injection layer 47, the hole transporting layer 48, thelight-emitting layer 49, the electron injection layer 51, and the secondelectrode 52 in that order from the bottom layer, wherein thecrystalline molecules have an orientation that is greater than or equalto 1 degree and less than or equal to 90 degrees with respect to thesubstrate 45.

With this arrangement, when cohesion molecules having such anorientation are incorporated, the injection rate of the first metalelectrode 46 and the hole injection layer 47 improves, thereby making itpossible to decrease the driving voltage to be applied between the firstmetal electrode 46 and the second electrode 52.

Further, in the organic semiconductor device 3 of the above-describedembodiment, in addition to the aforementioned configuration, thecohesion molecules employed may be of an organic material [C₆₀(fullerene), carbon nanotube, Alq₃, etc.], fluoride material (lithiumfluoride, etc.), metal oxide (MoOx, WoOx, TiOx, ZnOx, etc.), gaseousmolecules (oxygen, etc.), self-assembled film (SAM film, etc.), metal,or oxide nano-colloid.

With this arrangement, the driving voltage to be applied between thefirst metal electrode 46 and the second electrode 52 decreases, makingit possible to extend the service life of the organic semiconductordevice 3.

Further, in the organic semiconductor device 3 of the above-describedembodiment, in addition to the aforementioned configuration, the seriesof discontinuous clusters is a thin film having a rate of coverage ofthe top surface of the first metal electrode 46 that is greater than orequal to 1% and less than 100%.

With this arrangement, it is possible to maintain electric continuitywith the first metal electrode 46 and the hole injection layer 47 whilereducing the driving voltage to be applied between the first metalelectrode 46 and the second electrode 52.

Further, in the organic semiconductor device 3 of the above-describedembodiment, in addition to the aforementioned configuration, thelight-emitting layer 49 outputs visible light from the electric fieldcorresponding to the voltage applied between the first metal electrode46 and the second electrode 52.

With this arrangement, the crystallinity controlling member 5 or 7controls the orientation in accordance with the surface roughness of theuneven top surface of the hole injection layer 47 that is positionedalong the surface that comes in contact with the first metal electrode46. As a result, holes are removed from the first metal electrode 46 andreadily moved to the hole injection layer 47, making it possible todecrease the overall driving voltage of the organic semiconductor device3 to a greater degree than in prior art, even when visible light isoutputted at a level similar to prior art. Further, since the organicsemiconductor device 3 operates at a low driving voltage, the burdenplaced on the device itself is alleviated, thereby extending the servicelife of the device further than in prior art.

The display panel of the above-described embodiment comprises theorganic semiconductor device 3 including, between a pair of electrodesof the first metal electrode 46 (anode) and the second electrode 52(cathode), at least, the light-emitting layer 49, the hole injectionlayer 47 which removes holes from the first metal electrode 46, the holetransporting layer 48 formed on a side of the first metal electrode 46(anode) from the light-emitting layer 49 for transporting the holesremoved by the hole injection layer 47 to the light-emitting layer 49,and the electron injection layer 51 formed on a side of the secondelectrode 52 from the light-emitting layer 49 for removing electronsfrom the second electrode 52 and transporting the electrons thus removedto the light-emitting layer 49, wherein the organic semiconductor device3 further comprises on the top surface of the hole injection layer 47that is in contact with the first metal electrode 46 the crystallinitycontrolling member (cohesion matter, cohesion molecules) which is aseries of discontinuous clusters along the top surface of the holeinjection layer 47 in contact with the first metal electrode 46, forcontrolling the orientation of the crystalline molecules 9.

With this arrangement, the crystallinity controlling member 5 or 7controls the orientation in accordance with the surface roughness of theuneven top surface of the hole injection layer 47 that is positionedalong the surface that comes in contact with the first metal electrode46. As a result, the holes are removed from the first metal electrode 46and readily moved to the hole injection layer 47, making it possible todecrease the overall driving voltage of the organic semiconductor device3 of the display panel to a greater degree than in prior art. Further,since the organic semiconductor device 3 operates at a low drivingvoltage, the burden placed on the device itself is alleviated, therebyextending the service life of the device further than prior art.

Such a display panel with the built-in organic semiconductor device 3 iscapable of lowering the driving voltage of each of the organicsemiconductor devices 3, thereby making it possible to reduce theoverall power consumption. Furthermore, this display panel, in additionto the aforementioned configuration, further comprises each of thecomponents of the organic semiconductor device 3 of embodiment 1, makingit possible to achieve the same advantages as those of the organicsemiconductor device 3 having such a configuration.

Embodiment 2

Embodiment 2 describes an illustrative scenario in which a solar cellhas substantially the same configuration as the organic semiconductordevice shown in embodiment 1. Thus, the same reference numerals as thosein FIGS. 1 to 12 of embodiment 1 denote the same components andbehavior, and descriptions thereof will be omitted. The followingdescription will focus on the differences between the embodiments.

In the organic solar cell of embodiment 2, a photoelectric conversionlayer is used as the organic material in place of the light-emittinglayer 49 that exists in the organic semiconductor device 3 of embodiment1, at the same location as the light-emitting layer 49. Thisphotoelectric conversion layer has a function of separating the excitersgenerated on the boundary surface between the P-type material and N-typematerial that absorb light into holes and electric charges.

Additionally, this organic solar cell in its basic structure has anelectron transporting layer formed on a side of the cathode 52 (secondelectrode) of the photoelectric conversion layer, in place of theabove-described hole injection layer 47, hole transporting layer 48, andelectron injection layer 51 layered on the aforementioned organicsemiconductor device 3. This electron transporting layer has a functionof removing the electric charge from the photoelectric conversion layerand transporting that charge to the cathode 52.

The organic solar cell includes a crystallinity controlling member whichis a series of discontinuous clusters along the top surface of thephotoelectric conversion layer that is in contact with the anode 46(first metal electrode), for controlling the orientation of thecrystalline molecules. The crystallinity controlling member here is madeof the same material and components as those of the crystallinitycontrolling member 8 of embodiment 1, and has substantially the samefunction of improving the injection rate. That is, the crystallinitycontrolling member includes cohesion molecules such as C₆₀, for example.

Here, each layer of the organic solar cell, layered in the order of theanode 46, the crystallinity controlling member, the P-type material ofthe photoelectric conversion layer, the N-type material of thephotoelectric conversion layer, the electron transporting layer, and thecathode 52, employ materials such as described below. Note that aforward slash “/” indicates a boundary between layers.Au/C₆₀/CuPc/C₆₀/Alq₃/Ag

Note that the C₆₀ used as the N-type material (bulk) is a continuousfilm unlike the above-described crystallinity controlling member. TheN-type material of the above-described photoelectric conversion layerhas a function of a solar cell as well as a function of injectinggenerated holes into the anode 46.

Here, the P-type material of the aforementioned photoelectric conversionlayer is referred to as an organic electron donating material (ororganic electron donor layer). The material used for the organicelectron donor constituting this organic electron donor layer(hereinafter sometimes referred to as “p-type layer” as well) is notparticularly limited as long as the charge carrier is a hole and thematerial exhibits p-type semiconductor characteristics.

Specific examples of this organic electron donor include a macromoleculesuch as an oligomer or polymer having thiophene and derivatives thereofin its backbone, an oligomer or polymer having phenylenevinylene andderivatives thereof in its backbone, an oligomer or polymer havingvinylcarbazole and derivatives thereof in its backbone, an oligomer orpolymer having pyrrole and derivatives thereof in its backbone, anoligomer or polymer having acetylene and derivatives thereof in itsbackbone, an oligomer or polymer having isothianaphthene and derivativesthereof in its backbone, or an oligomer or polymer having heptadiene andderivatives thereof in its backbone; a low molecular weight moleculesuch as metal-free phthalocyanine or metal phthalocyanine andderivatives thereof, diamines or phenyldiamines and derivatives thereof,an acene such as pentacene and derivatives thereof, a metal-freeporphyrin or metal porphyrin such as porphyrin, tetramethylporphyrin,tetraphenylporphyrin, diazotetrabenzporphyrin,monoazotetrabenzporphyrin, diazotetrabenzporphyrin,triatetrabenzporphyrin, octaethylporphyrin, octaalkylthioporphyrazine,octaalkylaminoporphyrazine, aminoporphyrazine, hemiporphyrazine,chlorophyll, and derivatives thereof; or a quinone pigment such ascyanine pigment, merocya, benzoquinone, or naphthoquinone. The centralmetals of the metal phthalocyanine and metal porphyrin employed are eacha metal, metallic oxide, or metallic halide such as magnesium, zinc,copper, silver, aluminum, silicon, titanium, vanadium, chrome,manganese, iron, cobalt, nickel, tin, platinum, or lead. Note that, inparticular, an organic material wherein an absorption band exists in thevisible range (300 nm to 900 nm) is preferred.

On the other hand, the N-type material of the aforementionedphotoelectric conversion layer is also referred to as an organicelectron accepting material (or organic electron acceptor layer). Theelectron acceptor constituting this electron acceptor layer (hereinaftersometimes referred to as “n-type layer” as well) is not particularlylimited in this application as long as the charge carrier is an electronand the material exhibits n-type semiconductor characteristics.

Specifically, the electron donor of the organic electron acceptor layeremployed may be a macromolecule such as an oligomer or polymer havingpyridine and derivatives thereof in its backbone, an oligomer or polymerhaving quinoline and derivatives thereof in its backbone, a ladderpolymer based on a benzophenanthroline and derivatives thereof, orcyanopolyphenylenevinylene; or a low molecular weight molecule such as afluorinated metal-free phthalocyanine or fluorinated metalphthalocyanine and derivatives thereof, perylene and derivativesthereof, naphthalene derivatives, or bathocuproine and derivativesthereof. Other possibilities include a modified or unmodified fullereneor carbon nanotube. Note that, in particular, similar to theaforementioned case, an organic material wherein an absorption bandexists in the visible range (300 nm to 900 nm) is preferred.

In such an organic solar cell, the light that enters from an externalsource (hereinafter “external light”) passes through the transparentsubstrate 45 and the anode 46, and reaches the photoelectric conversionlayer. In this photoelectric conversion layer, light such as solar lightis absorbed through the use of an electron donating material or electronaccepting material having an absorption spectrum in the solar lightspectrum, for example.

When the light is absorbed by the electron donating material, forexample, exciters are generated, resulting in charge separation and thegeneration of electrons and holes. Of these, the electrons move to theelectron accepting material and, from the cathode 52, to the anode 46via an external electric circuit. The electrons that move to this anode46 bond with the holes generated in the electron donating material, andreturn to their original state. Through the repetition of such electronmovement, the organic solar cell removes electric energy from the anode46 and the cathode 52.

FIG. 14 and FIG. 15 are diagrams illustrating an example of the voltageand current density characteristics of the organic solar cell. FIG. 14illustrates an example of voltage and current density characteristics ofthe organic solar cell of embodiment 2, and FIG. 15 illustrates anexample of the voltage and current density characteristics of a generalorganic solar cell for comparison purposes.

In FIG. 14 and FIG. 15, the solid line represents a state wherein thesurrounding area of the organic solar cell is dark, and the dashed linerepresents a state wherein the surrounding area of the organic solarcell is light (irradiance level: 100 [nW/cm²]). Note that the horizontalaxis indicates voltage [V], and the vertical axis indicates currentdensity Id [mA/cm²]. Each parameter is as follows: ηisc=0.40 [%],Voc=0.45 [V], Jsc: 1.65 [mA/cm²], and FF: 0.53.

Material and Thickness of Each Layer of the Organic Solar Cell ofEmbodiment 2

In the organic solar cell of embodiment 2, Ag (15 nm)/C₆₀ (3 nm)/CuPc(40 nm)/C₆₀ (40 nm)/Alq₃ (10 nm)/Ag (50 nm) are layered in that orderfrom the anode 46 on the substrate 45. Note that the forward slash “/”indicates a separation between layers.

The organic solar cell of embodiment 2, as illustrated in FIG. 14,produces an electromotive force Vg [V] such as shown in the figure inaccordance with the difference in the number of photons between theaforementioned case where the surrounding area is dark (equivalent to“Dark” in the figure) and the aforementioned case where the surroundingarea is light (equivalent to “Light” in the figure). The electromotiveforce Vg [V] is thus produced as a result of the control of theorientation between the anode 46 and the hole transporting layer 48similar to embodiment 1.

Material and Thickness of Each Layer of the General Organic Solar Cell

In the general organic solar cell, Ag (15 nm)/CuPc (40 nm)/C₆₀ (3nm)/Alq₃ (10 nm)/Ag (50 nm) are layered in that order from the anode 46on the substrate 45. Note that the forward slash “/” indicates aseparation between layers.

On the other hand, the general organic solar cell, as illustrated inFIG. 15, exhibits minimal difference in the number of photons betweenthe aforementioned case where the surrounding area is dark (equivalentto “Dark” in the figure) and the aforementioned case where thesurrounding area is light (equivalent to “Light” in the figure), andtherefore does not produce an electromotive force Vg [V] as describedabove. The electromotive force Vg [V] does not occur since theorientation is not controlled between the anode 46 and the holetransporting layer 48.

The organic solar cell of the above-described embodiment 2 includes,between a pair of electrodes of the first metal electrode 46 (anode) andthe second electrode 52 (cathode), at least, the photoelectricconversion layer which separates the exciters generated at the boundarysurface between the P-type material and N-type material that absorblight into holes and electric charges, the electron transporting layerformed on a side of the second electrode 52 from the photoelectricconversion layer for removing electrons from the photoelectricconversion layer and transporting the electrons thus removed to thesecond electrode 52, wherein the organic solar cell further comprisesthe crystallinity controlling member 8 (5, 7) which is a series ofdiscontinuous clusters along the top surface of the photoelectricconversion layer in contact with the first metal electrode 46, forcontrolling an orientation of the crystalline molecules 9.

With this arrangement, the crystallinity controlling member 8 (5, 7)controls the orientation in accordance with the surface roughness of thetop surface thereof, making it easier to remove the electric charge fromthe photoelectric conversion layer and move the charge thus removed tothe cathode 52. As a result, the voltage temporarily produced betweenthe first metal electrode 46 and the second electrode 52 becomes higherthan that in prior art, making it possible to improve the overallluminous efficiency to a greater degree than prior art. Further, sincethe organic solar cell operates at a low driving voltage, the burdenplaced on the device itself is alleviated, thereby extending the servicelife of the device further than prior art.

In the organic solar cell of the above-described embodiment, the organicsolar cell comprises substantially the same components as the organicsemiconductor device 3 of the aforementioned embodiment 1, excluding thephotoelectric conversion layer in place of the light-emitting layer 49,and each achieves substantially the same advantages.

Note that the embodiments of the present invention are not limited tothe above, and various modifications are possible. In the following,details of such modifications will be described one by one.

In the above-described embodiments, LiF, for example, may be employed inplace of the aforementioned MoO₃, etc., as the aforementioned cohesionmolecules. Furthermore, α-sexithiophene (6T), for example, may be usedas the crystalline molecules 9.

While in the above-described embodiments the anode 46 is a transparentor semitransparent electrode, the present invention is not limitedthereto, allowing the anode 46 to be non-transparent.

While the above-described embodiments have been described in connectionwith an illustrative scenario in which gold (Au) is mainly used for theanode 46, the present invention is not limited thereto, allowing for useof the previously described oxide semiconductor of silver, copper, ITO,IZO, etc., as well as materials including platinum, molybdenum,aluminum, an inorganic compound, or fluoride.

In the above-described embodiments, an organic material such as C₆₀(fullerene), carbon nanotube, or Alq₃, a fluoride material such as LiF(lithium fluoride), a metal oxide such as MoOx, WoOx, TiOx, or ZnOx(where x is an integer), gaseous molecules such as oxygen, aself-assembled film such as a so-called SAM film, a metal, or an oxidenano-colloid may be alternatively selected as the aforementionedcohesion molecules.

The configuration of each of the organic semiconductor devices 3 of theabove-described embodiments may also be applied to a switch device or aso-called organic switch device that employs organic material. Examplesof such an organic switch device include an organic transistor, forexample. With this arrangement, the organic switch device is capable ofachieving substantially the same advantages as the aforementionedembodiments.

While in the above-described embodiments the orientation is controlledbetween the anode 46 and the hole transporting layer 48 therebydecreasing the driving voltage, the present invention is not limitedthereto, allowing the orientation to be controlled between the cathode52 and the electron transporting layer 50 in substantially the samemanner as the above-described embodiments, thereby decreasing thedriving voltage.

Note that, in the above-described embodiments, theorientation-controlled organic semiconductor is made of a material otherthan an amorphous material, and has a crystalline planar or bar-shapedmolecular structure.

In the above-described embodiments, the cohesion matter 5, such as thecohesion molecules, that partially covers the first metal electrode(anode) 46, does not necessarily have to be manufactured with a coverageof greater than or equal to 1% and less than 100% from the very start ofthe manufacturing process of the organic semiconductor device 3 or theorganic solar cell, allowing the flat cohesion matter 5 to be initiallymanufactured so that it covers the entire surface of the first metalelectrode 46 (coverage: 100%), for example, and then modified by etchingor scratching, for example, so that the coverage becomes less than 100%.

Furthermore, while in the above-described embodiments cohesion moleculesare incorporated into the top surface of the hole injection layer 47,etc., that faces the first metal electrode 46, the present invention isnot limited thereto, allowing for use of the same configuration betweenthe substrate 45 and the first metal electrode 46 to control theorientation, which achieves substantially the same advantages as theaforementioned embodiments.

In a case where the HOMO level of the cohesion molecules of theabove-described embodiments is near the HOMO level of the substrate 45or the HOMO level of the orientation-controlled crystalline molecules 9,the injection efficiency increases. The HOMO level of each material isAu (5.1 [eV]), CuPc (5.1 [eV]), pentacene (5.1 [eV]), MoO₃ (5.3 [eV],C₆₀ (6.0 [eV]), Alq₃ (5.9 [eV]), and LiF (>7 [eV]).

While in the above-described embodiments the top surface of the holeinjection layer 47 of the surface that comes in contact with the firstmetal electrode 46 is uneven in shape, the present invention is notlimited thereto, allowing for the existence of a nano-order structure(particle), for example. In such a case, the structure employed may be aso-called nano-pattern structure or a honeycomb structure. Thenano-pattern structure here refers to a state where particles of a sizeof a several nm are interspersed to form an uneven shape.

In the organic semiconductor device 3 or the organic solar cell of theabove-described embodiments, in addition to the aforementionedconfiguration, the above-described series of discontinuous clusters maybe a structure having an uneven shape.

With this arrangement, the existence of such a structure having anuneven shape increases the surface roughness of the top surface of thehole injection layer 47, etc., of the surface that comes in contact withthe first metal electrode 46, making it possible to lower the drivingvoltage to be applied between the first metal electrode 46 and thesecond electrode 52.

In the organic semiconductor device 3 or the organic solar cell of theabove-described embodiments, in addition to the aforementionedconfiguration, the above-described structure may employ a nano-patternstructure or a honeycomb structure.

With this arrangement, the existence of such a structure having anano-pattern structure or honey-comb structure increases the surfaceroughness of the top surface of the hole injection layer 47, etc., ofthe surface that comes in contact with the first metal electrode 46,making it possible to lower the driving voltage to be applied betweenthe first metal electrode 46 and the second electrode 52.

Further, examples of the high crystalline molecules (that is, moleculesof a material that does not readily become amorphous) in theabove-described embodiments include phthalocyanine derivatives includingCuPc, perylene derivatives such as PTCBI, fused polycyclic aromaticssuch as pentacene, and thiophene derivatives such as α-6T, and the like.Note that the high crystalline material is not necessarily limited tolow molecular materials, allowing for use of high molecular materialssuch as P3HT, for example.

Further, the aforementioned organic semiconductor device 3 may beemployed as a sensor as well since electric current modulation ispossible by irradiation of external light in a case where the anode 46and the cathode 52 are under positive voltage.

While in the above-described embodiments the organic semiconductordevice 3, etc., is layered in the order of the substrate 45, the anode46, the cohesion molecule layer, the hole injection layer 47, and thehole transporting layer 48, etc., the present invention is not limitedthereto, allowing for the layered structures below. Here, the term“cohesion molecules” refers to the section of the crystallinitycontrolling member 8 that is orientation controlled between the anode 46and the hole injection layer 47 of the above-described embodiments.

In the following illustrative examples of layered structures, only thelayered structure of the organic semiconductor device 3, etc., from theaforementioned substrate 45 to the location in front of the holeinjection layer 47, etc., is described while indicating a separationbetween layers by a forward slash “/”; all other layers including andfollowing the hole injection layer 48 are omitted for the sake ofsimplicity.

Layered example 1: substrate 45/cohesion molecule layer/metal layer(equivalent to the anode 46)

Layered example 2: uneven nano substrate (functioning as both thesubstrate 45 and the cohesion molecules; equivalent to the substrate45)/metal layer (the anode 46)

Layered example 3: substrate 45/uneven nano metal layer (equivalent tothe anode 46)

Layered example 4: substrate 45/nano structure/metal layer (equivalentto the anode 46)

Layered example 5: substrate 45/metal layer (equivalent to the anode46)/nano structure

Note that, in the above-described embodiment, in a case where the planarcohesion molecules, for example, are incorporated by deposition, thedeposition speed of the cohesion molecules may vary in a predeterminedform.

While the above-described embodiments have been described in connectionwith illustrative scenarios in which the thickness T of thecrystallinity controlling member 8 is 3 nm, the present invention is notlimited thereto, allowing for other preferred thicknesses according tothe relationship between each layer.

What is claimed is:
 1. An organic semiconductor device, comprising: afirst metal electrode; a hole injection layer comprising a plurality ofcrystalline molecules; a hole transporting layer; a light-emittinglayer; an electron injection layer; a second electrode; and acrystallinity controlling member which is a series of discontinuousclusters along a contact surface of the hole injection layer in contactwith the first metal electrode, for controlling an orientation of thecrystalline molecules of the hole injection layer, the crystallinitycontrolling member being a plurality of cohesion molecules that differfrom the crystalline molecules of the hole injection layer, wherein thefirst metal electrode, the hole injection layer, the hole transportinglayer, the light-emitting layer, the electron injection layer, and thesecond electrode are layered on a substrate in that order from a surfaceof the substrate, the hole injection layer removing holes from the firstmetal electrode, the hole transporting layer supplying holes removed bythe hole injection layer to the light-emitting layer and each of thecrystalline molecules has an orientation greater than or equal to 1degree and less than or equal to 90 degrees with respect to thesubstrate.
 2. The organic semiconductor device according to claim 1,wherein: said crystallinity controlling member controls the crystalorientation of at least one of planar molecules and bar-shaped moleculesas said crystalline molecules.
 3. The organic semiconductor deviceaccording to claim 1, wherein: MoO₃ is incorporated as said cohesionmolecules.
 4. The organic semiconductor device according to claim 1,wherein: C₆₀ is incorporated as said cohesion molecules.
 5. The organicsemiconductor device according to claim 1, wherein: Alq₃ is incorporatedas said cohesion molecules.
 6. The organic semiconductor deviceaccording to claim 3, wherein: said first metal electrode contains gold,silver, or copper.
 7. The organic semiconductor device according toclaim 6, wherein: said hole injection layer contains CuPc.
 8. Theorganic semiconductor device according to claim 6, wherein: said holeinjection layer contains pentacene.
 9. The organic semiconductor deviceaccording to claim 1, wherein: said cohesion molecules are one of anorganic material, fluoride material, metal oxide, gaseous molecules,self-assembled film, metal, or oxide nano-colloid.
 10. The organicsemiconductor device according to claim 1, wherein: said series ofdiscontinuous clusters is a thin film having a rate of coverage of a topsurface of said first metal electrode of greater than or equal to 1% andless than 100%.
 11. The organic semiconductor device according to claim1, wherein: said series of discontinuous clusters is a structure havingan uneven shape.
 12. The organic semiconductor device according to claim11, wherein: said structure has a nano-pattern structure or honeycombstructure.
 13. The organic semiconductor device according to claim 1,wherein: said light-emitting layer outputs visible light by an electricfield in accordance with an applied voltage between said first metalelectrode and said second electrode.